Advanced Arranger's Self-Guided Workshop Book
If you're interested in learning more about arranging... and great "tools" to use, I've put together an 88 page advanced, hands-on, self-guided Workshop Book with many examples and exercises which should prove to be fun to work through. All you need beside the book is a piano or midi keyboard, a pencil,... and a desire to improve your arranging skills.
A computer based music sequencing app. would be an optional (but handy) tool for recording and playing back your completed "arranging" exercises. Here's a link to 5 FREE music production Apps.